Lemon Buttermilk Pie

INGREDIENTS

• 1/2 cup butter
• 2/3 cup sugar
• 3 eggs, separated
• 1/2 teaspoon salt
• 1 teaspoon grated lemon, rind of
• 2 tablespoons lemon juice
• 3 tablespoons cornstarch
• 2 cups buttermilk
• 1 9" unbaked pie shell